The present invention relates generally to a device for repelling insects. More particularly, the present invention relates to an ultrasonic humidifier for dispersing insect repellant into the air.
Many types of insects and other nuisance bugs are considered pests, because they transmit diseases, damage structures or destroy agricultural products. Parasitic insects, such as mosquitoes, biting flies (black and greenhead), no-see-ums, lice, chiggers, ticks and bedbugs are notorious for decreasing the enjoyment of the out-of-doors for humans and pets alike. The options for pest control are generally limited to killing/capturing or repelling techniques.
Nuisance pests are typically killed through the application of a pesticide, such as by misting an area (see for example U.S. patent Ser. No. 11/524,073 to Modlin, et al. filed Sep. 20, 2006 and entitled “Automated Pest Misting System with Pump,” assigned to the assignee of the present invention, which is incorporated herein in its entirety), or through the use of bait and trap systems such as fly strips, CO2/octenol traps or electric bug zappers that attempt to attract pests with scent, heat, chemicals or light, or a combination of the above, and then either trap or kill pests that are lured to the bait. Each of these techniques has the unwanted detriment of killing beneficial insects, such as bees, butterflies, ladybugs and dragonflies, along with the nuisance insects. While there have been some advancements in biocontrol and in luring only nuisance insects to a trap, e.g., luring adult Japanese beetles into traps using beetle pheromones, generally it is difficult to attract unrelated types of nuisance insects to the exclusion of beneficial insects.
To date, one of the most effective method for repelling insects is by applying a coating of insect repellant containing synthesized DEET (n-n-diethylnetatoluamide) over exposed body parts and clothing which mosquitoes might penetrate. Currently DEET is the active ingredient in a wide range of repellants, such as creams, lotions, and aerosols. The disadvantages of using an insect repellant are many. For instance, the oily feel, they cause irritation to eyes, lips and other sensitive areas and can cause a skin reaction with some users, sometimes serious, and DEET is less effective in low concentrations, while higher concentrations may result in an increased risk of reaction. The product will often damage and/or stain certain plastics and fabrics and detractors often complain about the strong ‘chemical’ smell prevalent with DEET usage. Most people avoid using insect repellents around their home unless they intend to be outside for a prolonged period of time. Moreover, insect repellants are inconvenient and bothersome; they detract from the enjoyment with other people, such as on trips to the beach or camping, tailgating or picnicking.
Another, more convenient and environmentally friendly method for controlling nuisance pests in an area, is by application of a repellant throughout a control area. Although electronic repellants exist, such as by generating sound energy electronically at frequencies that repel insects, by far the most effective means is through the application of chemical repellants. Everyone has probably burned citronella to repel mosquitoes or heard of burning citronella in candles or torches or the like. Citronella candles and lamp fuel is relatively inexpensive, nontoxic and fairly easy to use. The active insect repelling ingredient in citronella, PMD (p-menthane 3,8-diol) has been demonstrated to repel mosquitoes, however, the recommended concentration of PMD is approximately ten percent and then citronella usually only repels mosquitoes for ten to twenty minutes. The reason that burning citronella is not always effective is that oftentimes the airborne concentration of PMD is very low, either because of the concentration being burned, or more probably because the dispersion pattern of the citronella fumes is not homogeneous in the control area. Insects do not breathe the way that mammals do and they do not have lungs, but instead they use tracheal respiration to transport air from spiracle openings on the surface of their bodies. Spiracles are located all along the insects' abdomens. It follows that the more effectively a repellent is dispersed in a control area, the more spiracles on an insect's body will receive the repellent. Burning citronella has been reported to form long airborne ‘spider webs’ when burned rather than a homogeneous concentration within the control area. Light breezes that do not affect mosquitoes sometimes move the citronella fumes completely out of the control area. Furthermore, it is difficult to meter the amount of citronella in the air, at best the user lights more or less candles or torches and repositions them in the control area for effectiveness.
Handheld trigger sprayers for broadcasting repellents are well known and widely used, especially around farm animals and in kennels and stables. Certain mosquito repellents are also sprayed from trigger or larger pump sprayers. However, these repellants are generally not meant to remain airborne, but are often applied to ground cover, yards, gardens and campgrounds. Typically, these repellents have an aromatic ingredient, such as concentrated garlic solution, that has some repelling properties, but actually kills most insects that come in contact with it. Automated misting systems, such as those disclosed in the Modlin application identified above, may be altered for dispersing repellents rather than insecticides. It should be mentioned that the Modlin device utilizes misting nozzles rather than spray nozzles. Spraying systems are less effective for repelling flying pests because the particle size ejected from a spray head is relatively large, usually greater than 50 microns, and therefore they do not remain suspended in the air for longer than a very few seconds. A mist has fewer open spaces or gaps between particles than a spray, and is generally less dense and will remain airborne longer than spray particles. Mist infers that the diameter of the suspended liquid is generally between 30 microns and 50 microns.
While misting systems are much more effective for dispensing repellents, the repellent mist will eventually fall out of the air and lose its effectiveness. What is needed is a safe and effective repellant dispersion system for use out-of-doors.